CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
CONSOLIDATED BALANCE SHEETS
Properties held-for-sale, accumulated depreciation and amortization (in dollars)	$ 613	$ 2,263
Mortgage loans receivable, allowance for doubtful accounts (in dollars)	884	921
Straight-line rent receivable, allowance for doubtful accounts (in dollars)	696	680
Other assets related to properties held-for-sale, allowance for doubtful accounts (in dollars)	839	839
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	15,000	15,000
Preferred stock, shares issued	2,000	2,000
Preferred stock, shares outstanding	2,000	2,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	60,000	60,000
Common stock, shares issued	30,445	30,346
Common stock, shares outstanding	30,445	30,346
Straight-line rent receivable from a lessee that qualifies as a related party (in dollars)	3,130	3,060
Marketable securities issued by an entity that qualifies as a related party (in dollars)		$ 6,500